Intermediate transfer belt and image forming apparatus adopting the belt

Abstract

The present invention concerns an image forming apparatus for forming a toner image on a transfer medium by use of an intermediate transfer belt, and also the intermediate transfer belt itself. The intermediate transfer belt has an elastic layer JIS-A hardness of which is 85° or less and at least one covering layer formed on the elastic layer. A relative permittivity ε and thickness t (μm) of the at least one covering layer satisfy relations of ε≦6 and t≧ε, and the intermediate transfer belt includes a fiber. The effects of this ε value and the fiber inside enabled to suppress scattering of toner well.

What is claimed is: 
     
       1. An image forming apparatus for forming a toner image on a transfer medium by use of an intermediate rotary member, comprising: an image bearing member;   toner image forming means for forming a toner image on the image bearing member;   an intermediate transfer belt for moving on an endless basis in contact with the image bearing member;   first transfer means for primarily transferring the toner image formed on the image bearing member onto the intermediate transfer belt at a first transfer position of the intermediate transfer belt; and   second transfer means, provided between the intermediate transfer belt and the first transfer means, for secondarily transferring the toner image having been transferred onto the intermediate transfer belt, onto the transfer medium at a second transfer position of the intermediate transfer belt;   wherein said intermediate transfer belt has an elastic layer JIS-A hardness of which is 85° or less and at least one covering layer formed on said elastic layer; relative permittivity e and thickness t (μm) of said at least one covering layer satisfy the following relations:   ε≦6 and t≧ε; and     the intermediate transfer belt comprises a fiber.     
     
     
       2. An image forming apparatus according to claim 1, wherein said intermediate transfer belt comprises the fiber arranged in a spiral form along a direction of movement of the intermediate transfer belt. 
     
     
       3. An image forming apparatus according to claim 2, wherein a surface for supporting toner having been transferred onto said intermediate transfer belt has sufficient releasability from the toner. 
     
     
       4. An image forming apparatus according to either one of claims 1 to 3, wherein volume resistivity of said elastic layer is 1×10 11  Ωcm or less. 
     
     
       5. An image forming apparatus according to either one of claims 1 to 3, wherein said image bearing member is an electrophotographic photosensitive member, and an outermost layer of said photosensitive member contains fine powder of tetrafluoroethylene resin. 
     
     
       6. An image forming apparatus according to claim 4, wherein said image bearing member is an electrophotographic photosensitive member, and an outermost layer of said photosensitive member contains fine powder of tetrafluoroethylene resin. 
     
     
       7. An image forming apparatus according to claim 6, wherein said toner is non-magnetic one-component toner. 
     
     
       8. An image forming apparatus for forming a toner image on a transfer medium by use of an intermediate rotary member, comprising: an electrophotographic photosensitive member;   toner image forming means for forming a toner image on the electrophotographic photosensitive member;   an intermediate transfer belt for moving on an endless basis in contact with the electrophotographic photosensitive member;   a first bias applying unit for forming a first transfer bias between said electrophotographic photosensitive member and the intermediate transfer belt, for primarily transferring the toner image formed on the electrophotographic photosensitive member onto the intermediate transfer belt at a first transfer position of the intermediate transfer belt; and   a second bias applying unit for forming a second transfer bias between the intermediate transfer belt and a transfer unit, for secondarily transferring the toner image having been transferred onto the intermediate transfer belt, onto the transfer medium at a second transfer position of the intermediate transfer belt;   wherein said intermediate transfer belt has an elastic layer JIS-A hardness of which is 85° or less and at least one covering layer formed on said elastic layer, wherein relative permittivity e and thickness t (μm) of said at least one covering layer satisfy the following relations:   ε≦6and t≧ε; and     the intermediate transfer belt comprises a fiber.     
     
     
       9. An image forming apparatus according to claim 8, wherein said intermediate transfer belt comprises the fiber arranged in a spiral form along a direction of movement of the intermediate transfer belt. 
     
     
       10. An image forming apparatus according to claim 9, wherein a surface for supporting toner having been transferred onto said intermediate transfer belt has sufficient releasability from the toner. 
     
     
       11. An image forming apparatus according to either one of claims 7 to 9, wherein volume resistivity of said elastic layer is 1×10 11  Ωcm or less. 
     
     
       12. An image forming apparatus according to either one of claims 7 to 10, wherein an outermost layer of said photosensitive member contains fine powder of tetrafluoroethylene resin. 
     
     
       13. An image forming apparatus according to claim 11, wherein an outermost layer of said photosensitive member contains fine powder of tetrafluoroethylene resin. 
     
     
       14. An intermediate transfer belt used in an image forming apparatus for forming a toner image on a transfer medium, said intermediate transfer belt having an elastic layer JIS-A hardness of which is 85° or less and at least one covering layer formed on said elastic layer, characterized by that relative permittivity e and thickness t (μm) of said at least one covering layer satisfy the following relations:   ε≦6 and t≧ε; and     the intermediate transfer belt comprises a fiber.   
     
     
       15. An intermediate transfer belt according to claim 14, said intermediate transfer belt comprising the fiber arranged in a spiral form along a direction of movement of the intermediate transfer belt. 
     
     
       16. An intermediate transfer belt according to claim 14 or 15, wherein a surface for supporting toner having been transferred onto said intermediate transfer belt has sufficient releasability from the toner. 
     
     
       17. An intermediate transfer belt according to either one of claims 14 to 15, wherein volume resistivity of said elastic layer is 1×10 11  Ωcm or less.